rx.h

This directory contains source code for tcpdump, a tool for network monitoring and data acquisition

 * SIZEs become set-once variables.  */

/* REMOTE_PACKET_SIZE is currently the same as local.  This is because REMOTE
 * is defined much too generally for my tastes, and includes the case of
 * multiple class C nets connected with a router within one campus or MAN.
 * I don't want to make local performance suffer just because of some
 * out-dated protocol that used to be in use on the NSFANET that's
 * practically unused anymore.  Any modern IP implementation will be
 * using MTU discovery, and even old routers shouldn't frag packets
 * when sending from one connected network directly to another.  Maybe
 * the next release of RX will do MTU discovery.
 */
#if 0
#define RX_MAX_DL_MTU  4352  /* what FDDI(RFC1188) uses... Larger? */
#define RX_MAX_DL_MTU 17914  /* what IBM 16MB TR  uses   */
#define RX_MAX_DL_MTU  8166  /* IEEE 802.4 */
#define RX_MAX_DL_MTU  4464  /* IEEE 802.5 MAX */
#define RX_MAX_DL_MTU  2002  /* IEEE 802.5 Recommended */
#endif

#define RX_MAX_DL_MTU           1500  /* what Ethernet uses */


#define RX_MAX_PACKET_SIZE      (RX_MAX_DL_MTU -RX_IPUDP_SIZE)
#define RX_HEADER_SIZE          sizeof(struct rx_header) /* Size of rx header */
#define RX_MAX_PACKET_DATA_SIZE (RX_MAX_PACKET_SIZE-RX_HEADER_SIZE)

#ifdef AFS_HPUX_ENV
  #define RX_LOCAL_PACKET_SIZE  (1497 - RX_IPUDP_SIZE)
  #define RX_REMOTE_PACKET_SIZE (1497 - RX_IPUDP_SIZE)
#else
  #define RX_LOCAL_PACKET_SIZE  RX_MAX_PACKET_SIZE  /* For hosts on same net */
  #define RX_REMOTE_PACKET_SIZE RX_MAX_PACKET_SIZE  /* see note above */
#endif

#if 0
#define RX_REMOTE_PACKET_SIZE   (576-RX_IPUDP_SIZE) /* For Internet hosts */
#endif

#define RX_PP_PACKET_SIZE       576                 /* tolerable SLIP */

#define RX_MINIMUM_PACKET_SIZE  (200-RX_IPUDP_SIZE)

/* Packet types, for rx_packet.type
 */
#define RX_PACKET_TYPE_DATA       1    /* A vanilla data packet */
#define RX_PACKET_TYPE_ACK        2    /* Acknowledge packet */
#define RX_PACKET_TYPE_BUSY       3    /* Busy: can't accept call immediately; try later */
#define RX_PACKET_TYPE_ABORT      4    /* Abort packet.  No response needed. */
#define RX_PACKET_TYPE_ACKALL     5    /* Acknowledges receipt of all packets */
#define RX_PACKET_TYPE_CHALLENGE  6    /* Challenge client's identity: request credentials */
#define RX_PACKET_TYPE_RESPONSE   7    /* Respond to challenge packet */
#define RX_PACKET_TYPE_DEBUG      8    /* Get debug information */
#define RX_PACKET_TYPE_PARAMS     9    /* exchange size params (showUmine) */

#define RX_PACKET_TYPES    { "data", "ack ", "busy", "abort", "ackall", \
                             "challenge", "response", "debug", "params" }
#define RX_N_PACKET_TYPES  10      /* Must agree with above list; counts 0 */

/* Packet classes, for rx_AllocPacket
 */
#define RX_PACKET_CLASS_RECEIVE   0
#define RX_PACKET_CLASS_SEND      1
#define RX_PACKET_CLASS_SPECIAL   2

#define RX_N_PACKET_CLASSES       3     /* Must agree with above list */


/* Maximum number of acknowledgements in an acknowledge packet
 */
#define RX_MAXACKS          255

/* The structure of the data portion of an acknowledge packet: An acknowledge
 * packet is in network byte order at all times.  An acknowledgement is always
 * prompted for a specific reason by a specific incoming packet.  This reason
 * is reported in "reason" and the packet's sequence number in the packet
 * header.seq.  In addition to this information, all of the current
 * acknowledgement information about this call is placed in the packet.
 * "FirstPacket" is the sequence number of the first packet represented in an
 * array of bytes, "acks", containing acknowledgement information for a number
 * of consecutive packets.  All packets prior to FirstPacket are implicitly
 * acknowledged: the sender need no longer be concerned about them.  Packets
 * from firstPacket+nAcks and on are not acknowledged.  Packets in the range
 * [firstPacket,firstPacket+nAcks) are each acknowledged explicitly.  The
 * acknowledgement may be RX_NACK if the packet is not (currently) at the
 * receiver (it may have never been received, or received and then later
 * dropped), or it may be RX_ACK if the packet is queued up waiting to be read
 * by the upper level software.  RX_ACK does not imply that the packet may not
 * be dropped before it is read; it does imply that the sender should stop
 * retransmitting the packet until notified otherwise.  The field
 * previousPacket identifies the previous packet received by the peer.  This
 * was used in a previous version of this software, and could be used in the
 * future.  The serial number in the data part of the ack packet corresponds to
 * the serial number oof the packet which prompted the acknowledge.  Any
 * packets which are explicitly not acknowledged, and which were last
 * transmitted with a serial number less than the provided serial number,
 * should be retransmitted immediately.  Actually, this is slightly inaccurate:
 * packets are not necessarily received in order.  When packets are habitually
 * transmitted out of order, this is allowed for in the retransmission
 * algorithm by introducing the notion of maximum packet skew: the degree of
 * out-of-orderness of the packets received on the wire.  This number is
 * communicated from the receiver to the sender in ack packets. */

struct rx_ackPacket {
    u_short bufferSpace;    /* Number of packet buffers available.  That is:
                             * the number of buffers that the sender of the ack
                             * packet is willing to provide for data, on this
                             * or subsequent calls.  Lying is permissable.
                             */
    u_short maxSkew;        /* Maximum difference between serial# of packet ack
                             * nowledged and highest packet yet received
                             */
    u_int32_t firstPacket;  /* The first packet in the list of acknowledged
                             * packets
                             */
    u_int32_t previousPacket; /* The previous packet number received (obsolete?) */
    u_int32_t serial;       /* Serial number of the packet which prompted the
                             * acknowledge
                             */
    u_char  reason;         /* Reason for the acknowledge of ackPacket,
                             * defined below
                             */
    u_char  nAcks;          /* Number of acknowledgements */

    u_char  acks[RX_MAXACKS]; /* Up to RX_MAXACKS packet acknowledgements,
                               * defined below
                               */
    /* Packets <firstPacket are implicitly acknowledged and may be discarded
     * by the sender.  Packets >= firstPacket+nAcks are implicitly NOT
     * acknowledged.
     * No packets with sequence numbers >= firstPacket should be discarded by
     * the sender (they may thrown out at any time by the receiver)
     */
};

/* Reason for acknowledge message
 */
#define RX_ACK_REQUESTED        1   /* Peer requested an ack on this packet */
#define RX_ACK_DUPLICATE        2   /* Duplicate packet */
#define RX_ACK_OUT_OF_SEQUENCE  3   /* Packet out of sequence */
#define RX_ACK_EXCEEDS_WINDOW   4   /* Packet sequence number higher than window; discarded */
#define RX_ACK_NOSPACE          5   /* No buffer space at all */
#define RX_ACK_PING             6   /* This is a keep-alive ack */
#define RX_ACK_PING_RESPONSE    7   /* Ack'ing because we were pinged */
#define RX_ACK_DELAY            8   /* Ack generated since nothing has happened since receiving packet */

/* Packet acknowledgement type
 */
#define RX_ACK_TYPE_NACK        0   /* I Don't have this packet */
#define RX_ACK_TYPE_ACK         1   /* I have this packet, although I may discard it later */

#define RX_ACK_REASONS " R2OWSKAD"

/* The packet size transmitted for an acknowledge is adjusted to reflect the
 * actual size of the acks array.  This macro defines the size
 */
#define rx_AckDataSize(nAcks) (sizeof(struct rx_ackPacket) - RX_MAXACKS + (nAcks))

#define RX_CHALLENGE_TIMEOUT    2   /* Number of seconds before another
                                     * authentication request packet is generated
                                     */

/* RX error codes.  RX uses error codes from -1 to -64.  Rxgen may use other
 * eeror codes < -64; user programs are expected to return positive error codes
 */

/* Something bad happened to the connection; temporary loss of communication
 */
#define RX_CALL_DEAD                (-1)

/* An invalid operation, such as a client attempting to send data after having
 * received the beginning of a reply from the server
 */
#define RX_INVALID_OPERATION        (-2)

/* An optional timeout per call may be specified
 */
#define RX_CALL_TIMEOUT             (-3)

/* End of data on a read
 */
#define RX_EOF                      (-4)

/* Some sort of low-level protocol error
 */
#define RX_PROTOCOL_ERROR           (-5)

/* Generic user abort code; used when no more specific error code needs to
 * be communicated.  For example, multi rx clients use this code to abort a
 * multi rx call
 */
#define RX_USER_ABORT               (-6)

/* Port already in use (from rx_Init)
 */
#define RX_ADDRINUSE                (-7)

#endif